A recent expert consensus report concluded that, ?Little is known about how well or under what conditions health innovations are sustained and their gains maintained once they are put into practice.?1 This report placed high priority on conducting return on investment (ROI) studies to determine how much is gained when effective programs are sustained, and cost-benefit trade-offs for effort required to sustain. Postpartum depression (PPD) is common and can have lasting consequences for mother and child. Outpatient clinics offering prenatal care are an opportune place to deliver PPD prevention services because most women visit while pregnant. ROSE is a group intervention to prevent PPD, delivered during pregnancy in outpatient prenatal settings. ROSE has been found to significantly reduce cases of PPD in multiple randomized trials in community prenatal settings with racially and ethnically diverse low-income pregnant women. Requests for ROSE training and recent policy changes supporting payment for comprehensive perinatal services to underserved populations suggest a context ripe for embedding ROSE in prenatal clinics long-term. Given the need for ROI studies about sustainment efforts and that ROSE is well-positioned for sustain- ment research, we propose a Sequential Multiple Assignment Randomized (SMART) Trial of the effectiveness and cost-effectiveness of a stepwise approach to sustainment of ROSE in 90 outpatient clinics providing prenatal care to pregnant women on public assistance in MI, NY, RI, PA, MA, and FL. In Year 1, all clinics will receive enhanced implementation as usual (EIAU; initial training + tools for sustainment). At the first time at which a clinic is determined to be at risk for failure to sustain (i.e., at 3, 6, 9, 12, 15 months), that clinic will be randomized to receive either: (1) no additional implementation support (i.e., EIAU only), or (2) low-intensity coaching and feedback (LICF). If clinics receiving LICF are still found to be at risk at subsequent assessments, they will be randomized to either (1) EIAU + LICF only, or (2) high-intensity coaching and feedback (HICF). Additional study follow-up interviews will occur at 18, 24, and 30 months, but no implementa-tion intervention will occur after 18 months. Outcomes include: 1. Sustainment of core program elements at each time point and total length of time ROSE services were provided and were provided with at least moderate fidelity. 2. Health impact (PPD rates over time at each clinic) and reach. 3. ROI (costs, cost-offsets, and cost-effectiveness) of each sustainment step. Hypothesized mechanisms include sustainment of clinical and organizational capacity to deliver core elements, and engagement/ownership. The study will also examine predictors, tailoring variables, and implementation processes to determine which kinds of clinics need which level of sustainment support and when. To our knowledge, this study will be the first randomized trial evaluating the ROI of a stepped approach to sustainment, a critical unanswered question in implementation science. It will also advance knowledge of implementation mechanisms and clinical care for an at-risk population.